Bis(2,3-dihalopropyl)2-cyanoalkyl-phosphonates

ABSTRACT

THE NEW COMPOUNDS BIS(2,3-DIHALOPROPYL) 2-CYANOALKYLPHOSPHONATES ARE DISCLOSED WHICH HAVE BEEN FOUND TO BE EFFECTIVE FLAME RETARDANTS FOR PLASTICS SUCH AS POLYMETHYL METHACRYLATE, CELLULOSE ACETATE, AND VISCOSE RAYON.

Arthur D. F. Toy, Stamford, Conn., and Kenneth I. Eilers. Irvington, N.Y., assignors to Stautfer Chemical Company, New York, N.Y.

No Drawing. Filed Sept. 21, 1970, Ser. No. 74,139 Int. Cl. C07f 9/40 U.S. Cl. 260940 Claims ABSTRACT OF THE DISCLOSURE The new compounds bis(2,3-dihalopropyl) Z-cyanhalkylphosphoriates are disclosed which have been found to be effective flame retardants for plastics such as polymethyl methacrylate, cellulose acetate, and viscose rayon.

The present invention relates to new fire retardant compounds which can be effectively used as fire retardant agents in all polymer systems and especially in cellulosic materials such as rayon and cellulose acetate and acrylic polymers such as polymethyl methacrylate.

BACKGROUND OF THE INVENTION Brominated diallyl and triallyl phosphates are well known in the prior art as evidenced by U.S. Pat. 2,574,- 515. Cyanoethyl phosphonate compounds are also Well known as evidenced by Pat. 2,844,558. The 0,0di-npropyl Z-cyanoethylphosphonates are also known as evidenced by Pat. 2,754,320. Of these compounds, the brominated triallyl phosphate compound appears to be the most elfective. These compounds require an extremely large quantity of chemically combined bromine to be effective as flame retardants.

It has now been found that a flame retardant compound can be prepared with a lesser amount of bromine which is as effective as brominated triallyl phosphate and which compound shows an effective utility in flame retarding various polymer composition-s, particularly the modified cellulose compositions and polymethyl methacrylate.

The invention In accordance with the present invention, there are provided the new fire retardant agents (2,3-dihalopropyl) Z-cyanoalkylphosphonates which can be represented by the formula:

[Raiflioliiliaw wherein R and R independently represent hydrogen, C -C alkyl and C -C haloalkyl radicals (halo being derived from chlorine or bromine); R R R and R independently represent hydrogen and C -C alkyl radicals; and X and X are halogen radicals derived from chlorine or bromine; and the mixed alkyl and/or mixed halogen derivatives thereof. R R are preferably hydrogen and the halogen radical is preferably derived from bromine. These compounds at their specific level of bromine have been found to be as effective in flame retarding as other known compounds containing higher levels of bromine. Polymer systems including processed polymers which can take advantage of the flame retardant characteristics of these compounds include polyurethanes, cellulosics and modified cellulosics, polyamides, polyhalides, polyolefins, polyesters, acrylics, polyethers, polyacetals, epoxys, phenolics, polyphenylene oxide, and rubber.

The compounds of the present invention are bis(2,3- dihaloalkyl) Z-cyanoalkylphosphonates. The dihaloalkyl 3,745,197 tented July 10, 1973 groups are based on a normal propyl group, e.g., a carbon chain of 3, and which have halogens of either chlorine or bromine attached to both the 2 and 3 position of the propyl group. Mixed halogen derivatives such as 2-chloro, 3-bromo, are also included within the scope of the invention. In addition to hydrogen, the propyl group can also be substituted with other noninterfering organic groups. The terminal or number 3 carbon can be substituted with one or more lower alkyl radicals having from 1 to 4 carbons illustrated by methyl, ethyl, propyl, isopropyl, butyl, and isobutyl as well as with the corresponding halogen derivatives (chlorine and bromine). The haloalkyls can be illustrated by chloromethyl, chloroethyl, chloropropyl, chlorobutyl, and the corresponding bromine derivatives. The alpha and beta carbons can be substituted with a C -C lowar alkyl radical such as those given hereinbefore.

The cyano group is attached to the phosphorus atom by a 2 carbon atom chain. Two of, and preferably all of, the remaining valences of the carbon chain are hydrogen. One valence on each carbon can be substituted with a C -C lower alkyl radical.

Preferably, all the replaceable groups on both the ester and the cyano portion of the phosphonate are hydrogen. The halogen is preferably bromine.

The compounds of the present invention can be easily prepared by halogenating (chlorinating or brominating) diallyl-Z-cyanoethylphosphonate and derivatives thereof. These compounds are well known in the prior art. The methods for halogenating allylphosphates are also well known in the prior art and can be illustrated by those set forth in U.S. Pat. 2,574,515. This method of preparing the compounds of the invention is given as illustrative and applicants do not intend the invention to be limited thereby.

Illustrative of compounds within the scope of the pres ent invention are:

(1) bis(2,3-dichloropropyl) 2-cyanoethylphosphonate (2) bis(2,3-dibromopropyl) Z-cyanoethylphosphouate (3) [(2,3-dichloropropyl) (2,3-dibromopropyl)] 2- cyanoethylphosphonate (4) bis(2-chloro-3-bromo-propyl) 2-cyanoethylphosphonate (5) bis(2,3-dibromopropyl) 1-methyl-2-cyanoethylphosphonate (6) bis(2,3-dibromopropyl) 2-methyl-2-cyanoethylphos-= phonate (7) bis(2,3-dibromobutyl) 2-cyanoethylphosphonate (8) bis(2,3-dibromopentyl) Z-cyanoethylphosphonate (9) bis(2,3,6-tribromohexyl) 2-cyanoethylphosphonate (10') bis[2-(3,4-dibromobutyl)] 2-cyanoethylphosphonate ( 1 1) bis(2-methyl-2,3-dibromopropyl) Z-cyanoethylphosphonate These are given only as illustrative and it is not intended that the invention be limited thereto.

Compounds of the present invention are effective flame retardants for various polymer systems which include polyurethanes, either expanded or foamed and/ or in flexible or rigid forms; the cellulosics which include wood pulp, paper, fibre board and wood fibre as well as cotton and wool; modified celluloses such as cellulose acetate and rayon; olefin polymers such as polyethylene or polypropylene; natural and synthetic rubbers such as SBR (styrenebutadiene-rubber); epoxy polymers; polyesters; polyacrylates and their esters, amides and nitriles; polyvinyl acetals such as polyvinyl butyral; phenolics, polyethers such as polyethylene glycol; vinyl polymers such as polyvinyl chloride and the like. Extensive discussions of these polymers are well known in the prior art and can be more fully 3 found in various texts such as Polymers and Resins, Golding, D. Van Nostrand (1959) as well as Kirk-Othmer, Encyclopedia of Chemical Technology, 2d edition, by Inter-Science.

Of particular importance, it has been found that the 4 EXAMPLE 2 Preparation of bis(2,3-dichloropropyl) Z-cyanoethylphosphonate 'modified celluloses such as cellulose acetate and viscose 5 rayon can be effectively flame retarded by the use of the 2 compounds of the present invention. The compositions of (OHZCICHCICHZO)2P-CH2CII;CN the present invention can be applied directly to fabrics by padding, dipping, or spraying solutions or other such means in order to effectively provide an added on weight In a 2 liter round bottom fl k i d i h a Of from t0 y Weight- It is Preferred that the chancial stirrer and thermometer, and under which was tr at d mat r al C a t least 5% and Preferably from positioned a solid carbon dioxide/ acetone cooling bath, m 20% of the stated additive in order to provide was placed 124 grams .05 mole) of diallyl 2 ettective flame retarding re5iilt$- ethylphosphonate in 1 liter of methylene chloride and the The compounds of the Present invention a also mixture was cooled to below -10 0. Excess chlorine utilized y admixing with a P y e p i Prior (at least 81 grams corresponding to 0.57 mole chlorine to the formation of the polymer into its various forms per allyl group) was slowly admitted while maintaining such as fibres, films and the like. It is preferred for eitecthe temperature below c Aft the addition was fi flame Ietardahey to load e P y compositions complete, the reaction mixture was allowed to stand for With from t0 y Weight, of the iiame five minutes with the excess chlorine which was then tardant addltlve, Other materials such as plasticizers and purged with nitrogen The reaction mixture was then the like can also P for etteetlve Processing allowed to warm to room temperature. The reaction mixthe p y other ingredients Such as tillers, dyes, P ture was washed with a saturated sodium thiosulfate solu- Inehts, stahiiilel's and the like e also be Present in the 25 tion and the acidity removed by washing with a saturated P y Without adversely atieetlhg the heme Tetetdeiicysodium bicarbonate solution. As methylene chloride tends is This invention will be more fullyillustrated in the exto f an emulsion, the reaction mixture was washed amPleS which toilowwith a sodium chloride solution to break the emulsion. EXAMPLE 1 The methylene chloride layer was separated by adding anhydrous dried magnesium sulfate powder thereto. The Preparation Qf blstz3'dlbromopwpyl) methylene chloride layer was then filtered and the solvent z'cyanoethylphosphonate stripped in using a rotary vacuum solvent evaporator. The

structure of the product was confirmed by infrared spectral analysis. 0 b OtheIr compounds within the scope of the invention can a e easi rovide (CII2BrCHBrCHZO)Fl CH2CHZON in the gorllgoing dplbgcg ggyelng the phosphonate reactants EXAMPLE 3 Bis(2,3-dibromopropyl) 2-cyanoethylphosphonate was 40 Thefiame retardant compounds of the present invention prepared by placing 80 grams (0.37 mole) of diallyl 2- hlre lltlhZed and tested as follows: cyanoethylphosphonate and 300 milliliters of methylene Cellulose aeetate--The flame retardant Compounds of chloride in a one liter round bottom reaction flask Examples 1 and 2 are mixed in a 20 Weight Percent S0111- equippsd with a mechanical stirrer, thermometer and a tion of cellulose acetate in an 80/20 acetone/methanol nitrogen purge and a solid'carbon dioxide-acetone cooling Solvent y e he Solution is then cast into a 15 mil bath. The flask was also equipped with an addition funnel Sheet and air dried for 1 hour followed y an Oven containing about 118 grams (0.38 mole) of bromine and t g h 080 C. for about 1 hour. The fire retardant 200 milliliters of methylene chloride. The bromine soluused 111 such an amount that the final y film contains a tion was added slowly to the phosphonate over a two hour given P ge of fire retardant based on the y Weight period maintaining the temperature of the reaction of the acetate. Strips are then cut from the for testing. mass at below 40 C. Upon completion of the addition Viscose y 8 Samples of fire retardant f the reaction mass was allowed to warm to room tempera- Examples 1 and 2 are dissolved in a Solvent such as ditum Excess bromine was removed b hi h chloromethane and known weights of viscose rayon staples action mass with 200 milliliters of saturated sodium thioare alterhetely pp into the Solution and air dried until lf t solution. The acidity of h reaction mass was all the solution is consumed. The treated staples are then moved by washing with 200 milliliters of saturated sodium air dried Over g manually carded homogeneity carbonate solution. After layer separation the product and tested for flame rethlfdtlheylayer was h d ith illilit f t Th 'prod- The samples of cellulose acetate and viscose rayon as not layer slowly separated and the solvent was removed 0 P p above are tested for flame Tetaidaney y igniting from the yellow-green product by evaporation in a rotary the S me in a bunsen burner flame. The ratings are evaporation flask, the vacuum being applied for 48 hours. Objective and T1111 from Group A (p to D The structure was confirmed by elemental, infrared and Borderline results are given mixed ratings which Overlap nuclear magnetic resonance analytical techniques. two P TABLE I Polymer substrate Cellulose acetate Viscose rayon (5 grams) Fire retardant 2.5% 5.0% 10% 0.15 g. 0.3 g. 0.6 g.

Product of Example 1- (OHgBrCHBrCI-IgOhP(O)CH2CHaON C-D D C-D D Product of Example 2- (CH:CICHCICH O)2P(O)CHzCHzCN B C C-D B B-G B-C NorE.-A=Flammab1o; B Partially Flammable; O Partially Self-Extinguishing; D Self Extinguishing.

EXAMPLE 4 The flame retardant additives of the present invention were combined with polymethyl methacrylate and tested as follows:

Polymethyl methacrylate.-Samples of fire retarded polymethyl methacrylate (PMMA) are prepared by dissolving the proper amount of the flame retardant in 100 grams of methyl methacrylate containing 0.04 gram of a polymerization catalyst (azobisisobutylronitrile). The resulting solutions were poured into tubular molds and bulk polymerization was initiated by heating the solutions to a temperature of between about 85-90 C. The polymerization was allowed to proceed for a period of about 16 hours. yielding solid polymer rods having a diameter of mm.

The fire retardancy of these rods was then quantitatively evaluated by determining their Limiting Oxygen Index (LOI) by means of the procedure described in Fenirnore and Martin the November 1966 issue of Modern Plastics. In brief, this procedure directly relates flame retardancy to a measurement of the minimum percentage concentration of oxygen in an oxygemnitrogen mixture which permits the sample to burn; the LOI being calculated as follows:

Thus, a higher LOI is indicative of a higher degree of flame retardancy.

The following table presents the results of this evaluation.

1 LOI=Limiting oxygen index or percent oxygen at which value the sample will burn for less than 3 minutes when ignited in a G. E. Candle Tester. Values are =l=.3. I

2 Loadings are ercent, by weight, based on the weight of the polymethyl methacry ate.

The compound of Example 1 provided the same flame proofing characteristics to the polymethyl methacrylate at 10% and 20% loadings as brominated triallyl phosphate. Specifically, at 10% loadings the compound of Example 1 provided an LOI of 20.85 as against 20.1 for the brominated triallyl phosphate. At 20% loadings the compound of Example 1 provided an LOI of 22.0 as against 22.5 for brominated triallyl phosphate. The control with no flame retardant gave an LOI of 17.7.

These results show that the compounds of the present invention which contain 60% bromine and 5.8% phosphorus are as effective as compounds of the prior art containing 68.7% bromine and 4.5% phosphorus. That it would be expected that the compounds of the present invention would not be as effective due to the large fire retardant advantage generally conferred by the bromine atom on a fire retardant compound. The increased fire retardancy can not be attributed to the slight increase in the amount of phosphorus present in the compounds of the present invention. The increased fire retardancy can only be attributed to the synergistic eifect the nitrogen has on the phosphorus.

6 EXAMPLE 5 In a manner similar to the preceding Example 4, rods of rigid polystyrene were prepared by bulk polymerizing grams of styrene with 5 grams of divinyl benzene in the presence of 0.5 gram of benzoyl peroxide as catalyst and the desired amount of flame retardant. These rods were tested for flame retardancy using the L.O.I. test given above with the following results:

1 LOI=Limiting oxygen index as defined above.

EXAMPLE -6 Films of cellulose acetate containing varying amounts of bis(2,3-dichloropropyl) Z-cyanoethylphosphonate were prepared according to the method of Example 4 using pure acetone as solvent. The Limiting Oxygen Index for these films was determined with the following results:

TABLE IV Fire retardant 5% 10% Blank 18 (CHzClCHCiCH2O)2P(O)CHzCHzCN 19 28 20.01

Thus all types of both synthetic and naturally derived polymers and compounded polymers may be utilized in preparing fire retardant compositions using the fire retardant additives of the present invention.

All of the disclosed polymer systems are well known and each has extensive utilities well known to those skilled in the art. Some of the polymers are useful as fiber formers whereas others are used for molding compositions or are extruded to form various objects. The compositions of the invention can also be used equally as well for those well known utilities. The flame retardant additives can be used alone or in combination with other flame retardants. The flame retardants are incorporated in or on the polymer as may be appropriate for the form of polymer used. The additives can be incorporated in blends which are used for extrusion, milling injection molding and the like. The additives can be added to polymer solution which are used to cast films. Also, the additives can be added to spinning solutions such as in viscose rayon. The additives can also be coated onto preformed polymer shapes such as fiber batts, films, etc. This can be accomplished by padding, dipping, spraying (in an appropriate liquid medium) and the like. The fire retardant additives can be added to protective coatings generally applied to the exterior of a structure such as a polymer based paint. These are given only as illustrative of the numerous utilities for the compositions of the invention.

The invention is defined in the claims which follow.

What is claimed is:

1. Bis(2,3 dihalopropyl) cyanoethylphosphonates of the formula:

wherein R and R, independently represent hydrogen, C -C alkyl and C -C haloalkyl radicals; R R R and C independently represent hydrogen and C C alkyl 7 8 radicals; and X and X are halogen radicals derived from References Cited chlorine or bromine.

2. Bis(2,3-dihalopropyl) cyanoethylphosphonates as re- UNITED STATES PATENTS cited in claim 1 wherein said X and X halogen radicals 3,027,296 3/1952 Whetstone 260-951 3 2 3 fi i:1l21 $;s cyanoethylpho pho te 5 FOREIGN PATENTS 1s ,-1 s na sasrecited in claim 1 wherein said R R R R and R radi- 693742 7/1953 Great Bntam 260*940 Gals are hydrogen LEWIS GOTTS, Primary Examiner 4. Bis(2,3-dihalopropyl) cyanoethylphosphonates as recited in claim 1 wherein said phosphonate is bis(2,3-di- 10 RAYMOND, Assistant Examiner bromopropyl) 2-cyanoethylphosphonate. Us Cl XR 5. Bis(2,3-dihal0propyl) cyanoethylphosphonates as recited in claim 1 wherein said phosphonate is bis(2,3-di- 106-15 FP; 1260-45-7 936 ehloropropyl) Z-cyanoethylphosphonate. 

